Control slide valve for a hydraulic servo motor

ABSTRACT

A slide valve for the control of a hydraulic servo motor comprising a casing housing a slide member and providing at each end of the slide member a pressure chamber communicating, at one side with a pressure medium source and at the other with open air. The communication between each of the pressure chambers and the open air is effected through passages or bores extending longitudinally of axial extensions at each end of the slide member and is governed at the free ends of the slide member by members extending axially from a rod member which may be caused from the outside to move axially of the slide member.

11mm States Patent 1 1 1111 3,756,270

Mell 14 1 e e. A, W73

[ CONTROL SLIDE VALVE FOR A 3,013,539 l'2/l96l Rethmeier l37/625.69 x

Y AU HC SERVO MOTOR 3,027,880 4/1962 Van Den Bussche l37/625.63

Inventor: Knut Olav Melf, 6000 Alesund,

Norway Panissidi l37/625.64

Primary Examiner-Henry T. Klinksiek ['73] As'signeETKfM. I'JiiiaxT/t/S, ATEfiBHjNYWEi/ Attorney-watsem Cole. Gtindle & Watson 22 F] d: Ma 14 1972 1 r 57 ABSTRACT [21] Appl' 1 A slide valve for the control of a hydraulic servo motor "3 I comprising a casing housing a slide member and pro- 1 7 f??? W viding at each end of the slide member a pressure Mar. 16, Norway chamber communicating at one side a pre ure medium source and at the other with open air. The [52] US. Cl 137162563, l37/625.66, 91/384 communication between a h f th pr ssure cham- [51 Km. c1. Wl6k 11/07 bers and the p air is ecte roug passages or [58] Field of Search 137/6256, 625.63, beres extending longitudinally of axial extensiens at l37/625.66, 625.69, 625.68; 91/376, 384 each end of the slide member and is governed at the p free ends of the slide member by members extending [56] References cit d axially from a rod member which may be caused from UNITED STATES PATENTS the outside to move axially of the slide member. 2,922,400 1/1960 Lorence 91/384 X 6 Claims, 3 Drawing Figures 2,981,288 4/1961 Strader 9l/376 X P K5 )C-v 6 7 h J g 1 W I i V M 6 1 Q /7 PATENTED E 4 1 v SHEET 1 [IF 2 CONTROL SLIDE VALVE FOR A HYDRAULIC SERVO MOTOR The present invention relates to a control slide valve for a hydraulic servo motor, of the type in which a brake is associated with the slide member for the purpose of securing an accurate setting and arrest of the slide member by use of a negligible force, through the provision, at either end of the slide member of a pressure chamber defined by a cylinder formed in the valve casing and provided with an inlet for a pressure fluid, the pressure of which is lower than the operational pressure of the control slide valve.

In known devices of this type in which a pilot slide valve or a jet tube is used in order, at will, to put one or the other of the pressure chambers under pressure, it has been difficult to achieve that the control slide member is positioned in and maintained in stable intermediate positions.

According to the present invention such difficulties are avoided by the provision of passages or bores through an extension of reduced diameter at each end of the slide member, through which passages or .bores the individual pressure chambers may be put in communication with open air under the control of a memher which may be caused to move in the direction of the length of the slide member. By means of such a sys tem, the pressure in the pressure chamber, and consequently the actuation in one or the other direction, may be controlled from the outside, manually or preferably automatically in dependence upon the desired actuation of the control valve, so that the slide member is actuated in the same direction as the movement of the moved member and consequently follows the movements of the same.

The axial passages or bores, through which the individual pressure chambers may be set in communication with open air for the release of the pressure in the chamber in question, may be provided inthe slide member extensions proper and open out in the end face of the slide member extension in question, while the member which is to be moved by external influence is provided with a collar having a boundary surface extending parallelly to the said end face, the closing of the passages or bores being effected by the engagement of the appropriate collar to the end surface of the slide memberextension.However, it is also possible to arrange the passages in the form of axially extending cross sectional area restrictions of restricted length in the member which is to be moved by external influence, the end of each restriction situated most closely to the end face of the slidemember extension in question being closed by a collar on the movable member and of a diameter corresponding to that of the axial bore in the slide valve housing in which the member is movable, whereby a by far greater movability is obtained for the member which is to be influenced from the outside.

As indicated, a pressure chamber is provided at each end of the slide member, in order that the slide member may be operable by movement in both directions. In order hereby to obtain a simple, common controlof both pressure chambers, it is convenient that the members which are to be influenced from the outside for the adjustment of the pressure in the individual chambers, each through itsown set of bores or passages, are connected to a common rod which extends axially through the slide member and may be moved axially relatively to the same, to the effect that the pressures in both chambers are influenced simultaneously.

The enclosed drawings schematically illustrate how the valve of the invention may be constructed.

In the drawings, FIG. 1 is an axial longitudinal sectional view through a slide valve which at each end is provided with an arrangement according to the invention.

FIG. 2 is a corresponding sectional view, showing a second embodiment of the arrangement according to the invention.

FIG. 3 is a sectional view along the line Ill-Ill in FIG. 2.

in all figures, parts which correspond to each other are given the same reference numeral.

In the drawings, 1 is a cylindrical housing, accomodating a slide member 2 which is adapted to be moved axially relatively to the housing 1. The housing 1 is, in conventional manner, provided with an inlet duct3 for a pressure medium P, and has, together with the slide member 2, conventional annular grooves serving at will and in dependence of the position of the slide member 2 to feed the pressure medium to the two sides A and B, respectively of the piston d of a hydraulic servo motor 5, and to a sump through outlets R.

At each end, the slide member 2 is so shaped relatively to the housing 1 that in the neutral position of the slide member 2 two cylinder spaces 6 are formed between each end face 7 of the slide member and the corresponding face 8 of a closing member 10 in the housing 1. The slide member 2 is also provided with axial extensions '9 which are extending through the end members 10 in the housing 1, longitudinal passages 11 being provided in the extensions 9, serving to bring the spaces 6 in communication with the open air. On the other hand, each of the spaces 6 is in continuous communication with the pressure source P through a throttle valve 13, to the effect that when the slide member 2 is in the position shown in FIGS. 1 and 2, the neutral position, both spaces are under the same pressure, which is lower than the pressure P.

An axially extending rod 14 is carried freely through the slide member 2 and is, outside of each of the slide member extensions 9, provided with a collar 15 and, at one end operatively coupled to a motion mechanism 16, to the effect that the rod 14 with its collars 15 may be moved in a desired manner axially relatively to the slide member 2. The mechanism 16 and the hydraulic servo motor 4,5 are shown in FIG. 1 only, but corresponding systems are presumed to. be associated with the slide valve shown in FIG. 2.

In the embodiment of the valve which is shown in FIG. 1, the passages 11 are in the form of axial bores in the extensions 9, each opening out in the end faces 12 of the extensions. At the same time, the diameter of the collars l5 and the distance along the rod 14 between the collars are so related that when the slide member 2 is in the neutral middle position which is shown in the drawing, there is a slot between each of the end faces 12 and the corresponding collar 115, through which each of the spaces 6 is in free communi-. cation with open air. a

if new a-desired adjustment of the hydraulic servo motor 4,5 necessitates that the slide member 2 is moved to the right from the neutral middle position shown, such adjustment is effected by pulling the rod 14 to the right. Thereby the distance between the lefthand collar 15 and the corresponding end face 12 of the slide member extension 9 is reduced, and the free passage from the passages 11 is reduced, so that the pressure in the lefthand space 6 increases, to the effect that the face 7 of the slide member 2 is subjected to this increased pressure. The end face 12 is also subjected to the increased pressure, although to a very small degree.

At the same time, the communication passage from the righthand space 6 becomes correspondingly greater. Due to this difference in pressure between the lefthand and the righthand spaces 6, the slide member 2 is urged to the right and the piston 4 of the servo motor 5 is correspondingly influenced. When the piston 4 has performed the desired movement, the mechanism 16-17 causes, in conventional manner, that the slide member 2 is returned to the middle position, and the system is ready for a new adjustment.

In the embodiment of the system which is shown in H68. 2 and 3, the slide member extensions 9 are formed by means of inserted sleeves 91, and the axial passages are in the form of longitudinally extending flat, milled off portions of the surface of the rod 14, so that passages 111 are formed between the milled off faces of the rod and the inner surface of each of the sleeves 91. The passages 1 l1 communicate with the respective spaces 6 through radial bores 92 in the sleeves 91. Further, circumferential grooves 112 are cut out at each end of the passages 111, which grooves are defined by collars 151 and 152 on the rod 14 at the sides opposite to the openings of the passages 111. The distance along the rod 14 between the outer collars 151 is equal to the length of the slide member 2 with the extensions 9 of the same, to the effect that when the rod 14 is in the neutral middle position, as shown in FIG. 2, the side of each of the collars 151 which is facing the circumferential grooves 112, is on line with the free end face 12 of the corresponding slide member extension 9, to the effect that the communications between the spaces 6 and the open air are equally throttled by means of the collars lsl. The inner collars 152 serve both as terminations to the passages 111 and as guides for the rod 14 along the inner surface of the sleeve 91. The collars 151 are also made with the same diameter as the inner surface of the sleeve 91.

By a displacement in either direction of the rod 14, with its passages 111 and collars 151 and 152, one space 6 is kept closed while the other is in free communication with open air, the rod 14 being all the time during its movement perfectly guided in the sleeves 91. Consequently, the rod 14 has, in this case, a by far greater motion facility than the rod 14 of the embodiment of FIG. 1, inwhich embodiment the length of stroke of the rod is restricted by the difference between the length of the slide member 2 with its extensions and the axial distance between the collars 15. Thus, in the embodiment shown in FIG. 2, the rod may continue its axial motion when the face 7 at one end of the slide member 2 has abutted against the corresponding face 8 of the closing member 10, to the effect that a greater freedom in the construction of the return mechanism 16 is achieved I claim:

1. A control slide valve for a hydraulic servo motor of the type wherein a pressure chamber is provided at either end of the slide member for the purpose of setting the slide member position when the same is to be influenced for an adjustment of the hydraulic servo motor, each such pressure chamber being defined by an end face of the slide member and a cylinder surface formed in the slide valve housing and having an inlet for a medium of a pressure which is lower than the working pressure of the control slide valve, an axial extension of reduced diameter being provided at each end of the slide member and having at least one axially extending passage through which the foresaid individual pressure chambers are in communication with open air under the control of a member facing the external axial mouth of the passages and movable longitudinally of the slide member axis.

2. A valve as claimed in claim 1, wherein the axially extending passages open out in the end face of the slide member extension in question, while the member which may be caused to move axially is provided with a collar having a boundary surface which extends parallelly to such end face.

3. A valve as claimed in claim 1, wherein the axially extending passages are formed by a reduction of the cross sectional area of the member which may be caused to move axially, the end of each restriction which is closest to the end face of the slide member extension in question being terminated by a collar on the movable member having a diameter corresponding to the axial bore in the slide member within which the movable member may be moved.

4. A valve as claimed in claim 1, wherein the members which may be caused to move axially for the purpose of adjusting the flow section of the sets of axially extending passages are associated with one common rod which extends axially through the slide member and is longitudinally movable.

5. A valve as claimed in claim 1, wherein the axial distance between the collar surfaces each of which faces one of the two end faces of the slide member extensions is greater than the length of the slide member with its extensions.

6. A valve as claimed in claim 1, wherein the axial distance between the collars each of which terminates a set of sectional area restrictions is approximately equal to or or less than the length of the slide member with its extensions.

7 0- k a t e 

1. A control slide valve for a hydraulic servo motor of the type wherein a pressure chamber is provided at either end of the slide member for the purpose of setting the slide member position when the same is to be influenced for an adjustment of the hydraulic servo motor, each such pressure chamber being defined by an end face of the slide member and a cylinder surface formed in the slide valve housing and having an inlet for a medium of a pressure which is lower than the working pressure of the control slide valve, an axial extension of reduced diameter being provided at each end of the slide member and having at least one axially extending passage through which the foresaid individual pressure chambers are in communication with open air under the control of a member facing the external axial mouth of the passAges and movable longitudinally of the slide member axis.
 2. A valve as claimed in claim 1, wherein the axially extending passages open out in the end face of the slide member extension in question, while the member which may be caused to move axially is provided with a collar having a boundary surface which extends parallelly to such end face.
 3. A valve as claimed in claim 1, wherein the axially extending passages are formed by a reduction of the cross sectional area of the member which may be caused to move axially, the end of each restriction which is closest to the end face of the slide member extension in question being terminated by a collar on the movable member having a diameter corresponding to the axial bore in the slide member within which the movable member may be moved.
 4. A valve as claimed in claim 1, wherein the members which may be caused to move axially for the purpose of adjusting the flow section of the sets of axially extending passages are associated with one common rod which extends axially through the slide member and is longitudinally movable.
 5. A valve as claimed in claim 1, wherein the axial distance between the collar surfaces each of which faces one of the two end faces of the slide member extensions is greater than the length of the slide member with its extensions.
 6. A valve as claimed in claim 1, wherein the axial distance between the collars each of which terminates a set of sectional area restrictions is approximately equal to or or less than the length of the slide member with its extensions. 